1. Field of the Invention
This invention relates to an automatic document feeder for electric equipment, and more particularly to an automatic document feeder including an improved blocking mechanism.
2. Description of the Related Art
FIGS. 1, 2, and 3 show a conventional automatic document feeder 1 for electric equipment 100, which is disclosed in U.S. Pat. No. 6,893,013. The conventional automatic document feeder 1 includes an input tray 11, a feeding roller unit 12, and a blocking mechanism 13. The feeding roller unit 12 includes a shaft 121, and two feeding rollers 122, 123 sleeved on the shaft 121. 13. A compression spring 131, a C-shaped collar 132, and a driven arm 133 of the blocking mechanism 13 are sleeved on the shaft 121 between the feeding rollers 122, 123. The C-shaped collar 132 has two ends abutting respectively against the feeding roller 123 and the compression spring 131 so as to allow for co-rotation of the driven arm 133 with the shaft 121.
When the shaft 121 is rotated in a counterclockwise direction shown by the arrow in FIG. 1, the driven arm 133 pushes and rotates a first strip portion 135 of a blocking member 134 disposed pivotally on an inner end 111 of the input tray 11 in a clockwise direction. Hence, a second strip portion 136 of the blocking member 134 projects upwardly from the inner end of the input tray 11. That is, the blocking member 134 is disposed in a blocking position. In the blocking position, documents to be scanned can be placed onto the input tray 11 through an outer end 112 of the input tray 11 in such a manner that the leading ends of the documents abut against the second strip portion 136. Subsequently, when it is desired to pick one of the documents up, the shaft 121 is rotated clockwise, as shown in FIG. 2. Hence, the driven arm 133 is removed from the first strip portion 135. As a result, the blocking member 134 rotates by virtue of gravity to cause the second strip portion 136 to abut against a paper dam 14 so as to dispose the blocking member 134 in a non-blocking position, thereby allowing the one of the documents to be fed from the input tray 11.
The aforesaid conventional automatic document feeder 1 has the following disadvantages:    (1) Since the compression spring 131, the collar 132, and the driven arm 133 are sleeved on the shaft 121 between the feeding rollers 122, 123, the conventional automatic document feeder 1 is difficult to assemble.    (2) Since the shaft 121 is disposed under the input tray 11, the above-mentioned members connected to the shaft 121 are difficult to repair.    (3) The driven arm 133 occupies a large amount of space under the input tray 11. Thus, the length of a path for transferring the documents in the conventional automatic document feeder 1 is increased. As a result, the blocking mechanism 13 is not suitable for duplex document feeders.